Electronic Instrumentation Laboratory
Department of Microelectronics

Perishables Monitoring through Smart Tracking of Lifetime and Quality by RFID

Publications

  1. A 7μW Offset-and Temperature-Compensated pH-to-Digital Converter
    S. H. Shalmany; M. Merz; A. Fekri; Z. Y. Chang; R. J. O. M. Hoofman; M. A. P. Pertijs;
    Journal of Sensors,
    Volume 2017, Issue 6158689, January 2017. DOI: 10.1155/2017/6158689
    Abstract: ... This paper demonstrates a micropower offset- and temperature-compensated smart pH sensor, intended for use in battery-powered RFID systems that monitor the quality of perishable products. Low operation power is essential in such systems to enable autonomous logging of environmental parameters, such as the pH level, over extended periods of time using only a small, low-cost battery. The pH-sensing element in this work is an ion-sensitive extended-gate field-effect transistor (EGFET), which is incorporated in a low-power sensor front-end. The front-end outputs a pH-dependent voltage, which is then digitized by means of a co-integrated incremental delta-sigma ADC. To compensate for the offset and temperature cross-sensitivity of the EGFET, a compensation scheme using a calibration process and a temperature sensor has been devised. A prototype chip has been realized in a 0.16 μm CMOS process. It occupies 0.35 × 3.9 mm2 of die area and draws only 4 μA from a 1.8 V supply. Two different types of custom packaging have been used for measurement purposes. The pH sensor achieves a linearity of better than ±0.1 for pH values ranging from 4 to 10. The calibration and compensation scheme reduces errors due to temperature cross-sensitivity to less than ±0.1 in the temperature range of 6°C to 25°C.

  2. A 1.2-V 8.3-nJ CMOS humidity sensor for RFID applications
    Z. Tan; R. Daamen; A. Humbert; Y. V. Ponomarev; Y. Chae; M. A. P. Pertijs;
    IEEE Journal of Solid-State Circuits,
    Volume 48, Issue 10, pp. 2469‒2477, October 2013. DOI: 10.1109/jssc.2013.2275661
    Abstract: ... This paper presents a fully integrated CMOS humidity sensor for a smart RFID sensor platform. The sensing element is a CMOS-compatible capacitive humidity sensor, which consists of top-metal finger-structure electrodes covered by a humidity-sensitive polyimide layer. Its humidity-sensitive capacitance is digitized by an energy-efficient capacitance-to-digital converter (CDC) based on a third-order delta-sigma modulator. This CDC employs current-efficient operational transconductance amplifiers based on current-starved cascoded inverters, whose limited output swing is accommodated by employing a feedforward loop-filter topology. A programmable offset capacitor is included to remove the sensor's baseline capacitance and thus reduce the required dynamic range. To reduce offset errors due to charge injection of the switches, the entire system is auto-zeroed. The proposed humidity sensor has been realized in a 0.16- μm CMOS technology. Measurement results show that the CDC performs a 12.5-bit capacitance-to-digital conversion in a measurement time of 0.8 ms, while consuming only 8.6 μA from a 1.2-V supply. This corresponds to a state-of-the-art figure-of-merit of 1.4 pJ/conversion-step. Combined with the co-integrated humidity sensing element, it provides a resolution of 0.05\% RH in the range from 30\% RH to 100\% RH while consuming only 8.3 nJ per measurement, which is an order-of-magnitude less energy than the state-of-the-art.

  3. A 7μW pH-to-digital converter for quality monitoring of perishable products
    S. H. Shalmany; M. Merz; A. Fekri; Z. Chang; R. Hoofman; M. A. P. Pertijs;
    In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
    IEEE, pp. 1747‒1750, June 2013. DOI: 10.1109/Transducers.2013.6627125
    Abstract: ... This paper describes an energy-efficient smart pH sensor intended for use in RFID tags to monitor the quality of perishable products. The sensor is based on an Extended Gate Field-Effect Transistor (EGFET). In a measurement time of 20 ms, it achieves a pH resolution of 0.05 and an accuracy of 0.1 in a pH range from 3 to 10, while consuming only 7 μW. This level of power consumption, which is orders of magnitude lower than the prior art, is achieved by incorporating the EGFET in an ultra-low-power frontend based on a differential source-follower, and digitizing the resulting pH-dependent voltage using an incremental first-order ΔΣ ADC.

  4. A low-power CMOS integrated sensor for CO2 detection in the percentage range
    A. Humbert; B. J. Tuerlings; R. J. O. M. Hoofman; Z. Tan; D. Gravesteijn; M. A. P. Pertijs; C. W. M. Bastiaansen; D. Soccol;
    In Proc. International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS),
    IEEE, pp. 1649‒1652, June 2013. DOI: 10.1109/Transducers.2013.6627101
    Abstract: ... Within the Catrene project “PASTEUR”, a low-cost, low-power capacitive carbon dioxide sensor has been developed for tracking CO2 concentration in the percentage range. This paper describes this sensor, which operates at room temperature where it exhibits short response times as well as reversible behavior. It can be easily integrated using CMOS compatible processing, and has been combined with a Relative Humidity (RH) sensor, using the same capacitive transduction method, and with a low-power capacitance-to-digital converter, hence enabling correction of cross sensitivity to RH.

  5. Ultra-low Energy CMOS Humidity Sensors for RFID Applications
    Z. Tan; R. Daamen; A. Humbert; Y. V. Ponomarev; Y. Chae; G. C. M. Meijer; M. A. P. Pertijs;
    In Annual Sensor Technology Workshop Sense of Contact,
    The Netherlands, April 2013. (Best Poster Award).

  6. A 1.2 V 8.3 nJ energy-efficient CMOS humidity sensor for RFID applications
    Z. Tan; Y. Chae; R. Daamen; A. Humbert; Y. V. Ponomarev; M. A. P. Pertijs;
    In Dig. Techn. Paper IEEE Symposium on VLSI Circuits (VLSI),
    IEEE, pp. 24‒25, June 2012. DOI: 10.1109/vlsic.2012.6243771

  7. A 1.8V 11μW CMOS smart humidity sensor for RFID sensing applications
    Z. Tan; R. Daamen; A. Humbert; K. Souri; Y. Chae; Y. V. Ponomarev; M. A. P. Pertijs;
    In Proc. IEEE Asian Solid State Circuits Conference (A-SSCC),
    IEEE, pp. 105‒108, November 2011. DOI: 10.1109/ASSCC.2011.6123615
    Abstract: ... A fully-integrated humidity sensor for a smart RFID sensor platform has been realized in 0.16μm standard CMOS technology. It consists of a top-metal finger-structure capacitor covered with a humidity-sensitive layer, combined with a micro-power flexible sensor interface based on a second-order incremental delta-sigma converter. The interface can be easily reconfigured to compensate for process variation of the sensing element. In a measurement time of 10.2 ms, the interface performs a 13-bits capacitance-to-digital conversion while consuming only 5.85 μA from 1.8 V supply. In combination with the co-integrated sensor capacitor, it thus provides a humidity-to-digital conversion with a resolution of 0.1\% RH in the range of 20\% to 90\% RH at only 107 nJ per measurement. This represents a significant improvement in energy efficiency compared to existing capacitive-sensor interfaces with comparable performance.

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